The present invention relates to an image forming apparatus.
In a conventional image forming apparatus such as a printer, a copier, and a facsimile, an image is formed through the following process. First, a charge roller charges a surface of a photosensitive drum. An exposure device such as an LED head exposes the surface of the photosensitive drum to form a static latent image or a latent image thereon. A developing roller attaches a thin layer of toner to the static latent image to form a toner image. A transfer roller transfers the toner image to a sheet or a recording medium, thereby printing or forming an image on the recording medium. An image forming unit (developing device) is formed of the photosensitive drum, the charge roller, the developing roller, and the likes.
After transferring the toner image, the sheet is transported to a fixing device, so that the fixing device fixes the toner image to the sheet.
In the conventional image forming apparatus described above, an image is formed on the sheet under a specific condition such as a print speed, a fixing temperature, and the likes corresponding to the sheet. A temperature sensor is disposed adjacent to the photosensitive drum for detecting a temperature inside the image forming apparatus. When the temperature sensor detects a temperature higher than a specific temperature, the image forming apparatus temporarily stops the printing operation and performs an intermittent printing operation. Accordingly, it is possible to prevent a temperature inside the image forming apparatus from rising higher than the specific temperature, so that flow characteristic of toner is not deteriorated or the photosensitive drum is not charged improperly (refer to Patent Reference).
Patent Reference: Japanese Patent Publication No. 2004-309535
In the conventional image forming apparatus described above, when the temperature sensor detects a temperature below the specific temperature, the image forming apparatus performs the printing operation normally. However, when the image forming apparatus is installed in a relatively high temperature environment, discharging efficiency of heat of the image forming apparatus is lowered. Accordingly, a temperature inside the image forming apparatus may rise above the specific temperature rather quickly even in a normal condition.
As described above, the conventional image forming apparatus is configured to perform the intermittent printing operation until the temperature inside the intermittent printing operation becomes below the specific temperature. However, when the image forming apparatus is installed in a relatively high temperature environment, in which discharging efficiency of heat of the image forming apparatus is lowered, it may be difficult to maintain the temperature below the specific temperature even in the intermittent printing operation. As a result, the image forming apparatus may stay in a relatively high temperature environment for a long period of time, thereby deteriorating toner.
In view of the problems described above, an object of the present invention is to provide an image forming apparatus, in which it is possible to prevent toner from deteriorating due to exposure to a high temperature for a long period of time.
Further objects and advantages of the invention will be apparent from the following description of the invention.